Validity of a FBG-based smart sock system for measuring toe grip function in human foot

This study developed a smart sock system using optical fiber technology to measure the toe grip function of individual toes. The system comprised Fiber Bragg grating (FBG) sensors incorporated into a sock garment for measuring maximum toe flexion displacements. Calibration equation of each FBG sensor was determined from 3D motion capture system on 10 female subjects. The validity of the smart sock system was checked by comparing maximum toe flexion displacement against the gold standard of 3D motion capture. The root mean squared error was 0.95 (0.57) cm across 10 toes. The magnitude of toe displacement and error were similar between the left and right foot. In conclusion, the FBG-based smart sock system can successfully measure maximum toe flexion displacements of individual toes simultaneously. This system can be developed to support the evaluation of toe grip function in clinical and field settings.